Modeling Of Combustion Processes Research Articles

Overview of the Current State of Physical-Mathematical Modelling of Solid Fuel Combustion Processes

This study provides a comprehensive introduction to the combustion of solid propellants. We conduct a thorough review of existing physical-mathematical models related to solid fuel combustion processes. Additionally, we explore the heat propagation within the solid phase, examine the physical chemical processes in the k–phase, and investigate the fundamental solution of the heat conduction equation in a multiphase (k–phase) medium. The heat conduction equation plays a crucial role in governing the temperature distribution within a given material, and a profound understanding of its fundamental solution is essential for various engineering and scientific applications. In this research, we expand our analysis to a multiphase scenario, considering different phases with distinct thermal properties coexisting.

Исследование новой микрофакельной горелки с помощью программы Ansys Fluent

A study of a new micro-flame burner device (MFBD) for the combustion chamber of a gas turbine unit (GTU) using the Ansys Fluent program is presented. Research objective: determination of the optimal operating modes of the investigated burner, initial air parameters for maximum combustion efficiency, examination of the uniformity of the temperature field, and the concentration of nitrogen oxides in the combustion chamber of the gas turbine unit with the MFBD. The features of the design and operation of the micro-flame burner device are described, as well as the stages of modeling combustion processes in the Ansys Fluent software. The calculations conducted using various simulation parameters in this program allowed the evaluation of the efficiency of the new MFBD, determination of the temperature field distribution, and the nitrogen oxide content in the combustion products. The nitrogen oxide emissions in the combustion products during different modes of operation did not exceed 9 ppm. This data will be useful for further optimization and development of GTUs taking into account the requirements of efficiency and environmental safety. The presented study demonstrates the application of Ansys Fluent in the development of new technologies in the field of combustion and energy

Combustion efficiency control method of circulating fluidized bed boiler based on adaptive genetic algorithm

In order to improve the traditional boiler combustion efficiency control method, which has the problem of low efficiency after control, a new combustion efficiency control method of circulating fluidized bed boiler based on adaptive genetic algorithm is proposed in this paper. Firstly, the iterative principle of adaptive genetic algorithm is analyzed; Secondly, the combustion process model of circulating fluidized bed boiler is constructed by BP neural network method; Finally, based on the above model, the optimal control objective function of adaptive genetic algorithm is constructed, and the objective function is solved according to the iterative principle of adaptive genetic algorithm to complete the control of combustion efficiency of circulating fluidized bed boiler. The experimental results show that compared with the traditional control method, the combustion efficiency of the boiler controlled by this method is always more than 98%.

Modeling of chemical-looping combustion process of methane with nickel-based oxygen carrier

Modeling of chemical-looping combustion process of methane with nickel-based oxygen carrier

Assessment of the Possibility of Transition Power Boilers to Alternative Solid Fuels by Modeling Combustion Processes

Assessment of the Possibility of Transition Power Boilers to Alternative Solid Fuels by Modeling Combustion Processes

High temperature oxidation of residual oil pyrolysis intermediates for modeling gasification and combustion processes

Developing chemical kinetic models for residual oil pyrolysis, gasification, and combustion is very challenging due to the large number of components and molecular complexity. This study provides experimental data for model development and validation for two residual oils, heavy fuel oil (HFO) and vacuum residual oil (VRO). This study aims to identify and quantify the HFO and VRO pyrolysis intermediates and validate an oxidation chemical kinetic model of the pyrolysis intermediates to provide data for future residual oil model development using hybrid chemistry (HyChem) and functional groups for mechanism development (FGMech) approaches. The pyrolysis experiments were conducted in a bench-scale tubular reactor at atmospheric pressure and a temperature of 1273 K. Detailed compositions of the yields from the pyrolysis of HFO and VRO were analyzed using gas chromatography-flame ionization detection (GC-FID) for the gas yields and gas chromatography-mass spectrometry/flame ionization detection (GC–MS/FID) for the liquids. Elemental analysis was conducted for the solid residuals. The experiment results show similar pyrolysis products from HFO and VRO. A surrogate of major components of the gas products and representatives of benzene and naphthalene derivatives (major compounds identified in liquid products) of the liquid products was formulated and its chemistry was studied by measuring ignition delay times (IDTs) in a shock tube. IDT measurements were conducted for stoichiometric and rich (ϕ = 1 and 3) mixtures, pressures of 20 and 40 bar, and diluents of nitrogen and carbon dioxide. Brute force IDT sensitivity analyses were used to study the effect of pressure, equivalence ratio and diluents on the reactivity of the mixture.

Investigation on combustion efficiency of the hydrogen–oxygen mixture at various pressures and excess oxidizer based on experimental and theoretical studies

One of the ways to improve the efficiency of power plants, including nuclear power plants, can be the use of hydrogen energy complexes and hydrogen-oxygen steam generators in their composition. This is done by electrolysis production of hydrogen and oxygen and their further use in technological schemes of power units in the form of thermal energy. Fundamental in assessing the efficiency of such use of hydrogen technologies is the efficiency of hydrogen combustion in oxygen medium under different schematic-parametric conditions. In this paper combustion processes were studied in terms of evaluating efficiency of the hydrogen-oxygen mixture combustion at various pressures and an oxidizer excess. For this purpose, a calculation model of combustion processes of the hydrogen-oxygen mixture, including heat and mass transfer under the boundary conditions of the experiment was verified on the basis of the experimental data, obtained at 4-section flame tube. Has shown that increasing the pressure of the combustion products leads to a noticeable decrease in hydrogen underburning. The maximum effect is observed in the third section of the flame tube (a reduction by 56.72%), and the minimum effect is found in the first section (a reduction by 7.58%). In this case, the average specific reduction in hydrogen underburning in sections I-IV of the flame tube within the considered pressure ranged between 8.13, 17.41, and 31.34%/MPa, respectively. An increase in an oxidizer excess lead to a regular decrease in hydrogen underburning. In this case, the maximum decrease in hydrogen underburning is achieved with an oxidizer excess ratio of 2 in the third section of the flame tube (a reduction by 58.86%). At the same time, an increase in the positive effect of increasing pressure is observed. In this case, in the first two sections of the flame tube, the greatest dependence on the increase of an oxidizer excess ratio is observed. Thus, the maximum relative reduction in hydrogen underburning is achieved at the pressure of 6 MPa, and as a result amounts to 24.46% and 43.5% with the oxidizer excess ratio at 1.5 and 2, respectively.

Study of Scavenging and Combustion Processes for Small Two-Stroke Aviation Heavy Fuel Direct Injection Engines

Heavy-fuel aviation piston engines (HF-APEs) are widely used in general aviation and unmanned aerial vehicle (UAV) due to their safety and fuel economy. This paper describes a numerical and experimental study of scavenging and combustion processes on a 2-Stroke Direct Injected HF-APEs for light aircraft, with its cylinder specifically designed as cross scavenging. A 3-Dimentional transient model of in-cylinder flow and combustion process is established by the Forte platform, and the engine test system is set up. By comparing the simulation results to the experimental results, it showed that multi-ports cross scavenging can generate unbalanced aerodynamic torque in the cylinder. In the compression process, the swirl ratio (SR) gradually increases, and the peak SR reaches 15. Moreover, approximately 25% of exhaust residual gas in the cylinder is conducive to the fuel atomization and evaporation process in a high-altitude environment. When the injection timing is between −8 °CA and −16 °CA, the engine has the optimal power and economy performance at different altitudes. Finally, when the injection advance angle moves forward by 4 °CA, the maximum pressure increases by 2 MPa, with the rising rate decreasing gradually. The results have important significance for the development of the combustion system of small 2-Stroke Direct Injected HF-APEs.

Numerical modelling of heat transfer processes in coal-fired vortex furnace with bottom-port secondary blowing: ecological performance comparison for two types of coal fuel

The work is devoted to numerical 3D modelling of aerodynamics and pulverized-coal combustion processes in a novel vortex furnace of a boiler unit for thermal power stations. A prospective retrofitting design of this furnace, featuring additional tangential blowing at the bottom part of the vortex combustion chamber, has been studied. The firing regimes using two types of siberian coal (black coal, brown coal) are considered. Numerical results for the studied combustion regimes in the modified vortex furnace are presented, including the fields of velocity, temperature, species and dispersed phase concentrations, and the comparative analysis of NOx emissions for two types of coal.

Numerical Modeling and Experimental Investigation of Spray Combustion Process in Regenerative Liquid Propellant Mortar

AbstractRegenerative liquid propellant guns (RLPGs) have been studied for many years. However, the presence of large pressure oscillations is observed in almost each RLPG firing. In order to push forward the liquid propellant application in guns, a low pressure firing system called regenerative liquid propellant mortar (RLPM) is developed. The multiphase multidimensional fluid‐dynamics model is presented to research the interior ballistic properties of RLPM. A high‐speed liquid sheet spray model is presented for the annular jet in RLPM based on the linear stability analysis and surface wave breakup theory. In addition to the jet atomization, the droplets secondary breakup is considered. The experiments on a 60 mm RLPM test fixture are carried out, and the results indicate that the liquid propellant combustion oscillations are effectively suppressed. The spray and combustion processes have been simulated for the 60 mm RLPM which are in agreement with the experimental data well. Numerical results indicate an important benefit for the RLPM that the muzzle velocity is improved by increasing the charge quantity while the maximum chamber pressure remains unchanged.

Waste coal gasification fine slag disposal mode via a promising “efficient non-evaporative dewatering & mixed combustion”: A comprehensive theoretical analysis of energy recovery and environmental benefits

Coal gasification technology is an important starting source for the clean conversion and utilization of coal. Gasification fine slag (GFS) is the waste produced in the coal gasification process, its production and storage volume are increasing with the large-scale promotion of coal gasification technology. Currently, the GFS black water is processed by the horizontal belt filter and the moisture content of the obtained filter cake exceeds 50%, which has posed challenges to the environment and energy security. The study aims to solve the problems of environmental pollution and resource waste caused by high moisture GFS filter cake. The analysis of the basic physical properties of GFS and the recommendation of a high-efficiency dehydration technology of GFS under the combined action of “vacuum force-mechanical pressure-vibration force” was promoted, and the moisture of filter cake was reduced to 30% at lower energy consumption. By establishing a thermodynamic model, the quality and energy balance of GFS dehydration and mixed combustion process were studied, and the energy consumption and calorific value characteristics of mixed combustion in the two dehydration routes of “horizontal belt filter dehydration-high moisture filter cake mixed combustion” and “multi-energy field dehydration-low moisture filter cake mixed combustion” were compared. Based on comparing the energy consumption of multi-energy field dehydration and evaporation drying, the CO2 emission reduction was evaluated by unifying energy grades and a high-efficiency energy-saving path was analyzed. The studies showed that the GFS can be efficiently dehydrated through the multi-energy field, and the energy-saving is 47.3% compared with the current dehydration method. Through the establishment and analysis of thermodynamic models, it is found that the low-moisture GFS filter cake mixed combustion with coal has energy advantages. With standard coal consumption compared and CO2 emissions estimated, the multi-energy field dehydration technology reduces carbon dioxide emissions by 87.09% compared with evaporation drying. The research results will provide theoretical and technical support for the technical integration of efficient dewatering, carbon resource utilization and energy recovery of GFS.

Special Issue on Modelling, Simulation and Control in Combustion Processes of Renewable Fuels

The modeling and simulation of combustion processes is still a challenging field [...]

Laminar flame speed correlations for dual fuel flames in high-pressure conditions

The usage of methane as a fuel stands out as a transition strategy to zero carbon energy conversion processes. However, methane is difficult to be made to burn due to its strong molecular structure. To mitigate this issue, a mixture of methane and a more ignitable fuel may be a promising solution for large scale combustion applications. In many of those, the corresponding CFD setup can be very demanding and detailed chemistry may be replaced by simplified approaches, such as laminar flame speed methods. To contribute with robust and reliable modeling of combustion processes fueled by dual fuel mixtures, novel formulations are proposed to improve accuracy of laminar flame speed correlations. To accomplish this task, numerical simulations of 1D freely propagating laminar flames based on detailed chemistry are conducted for various pressures and equivalence ratios. Kinetic mechanisms are obtained from the literature and evaluated with available experimental data. For the best performing mechanism, the resulting laminar flame speeds are mapped based on fresh mixture composition and correlated through power-law wholly empirical equations. The proposed formulations show clear improvements when compared to other existing methods.

A machine learning framework for evaluating the biodiesel properties for accurate modeling of spray and combustion processes

The environment-friendly nature of biodiesel coupled with its inherent compression ignition fuel characteristics like better ignition quality, and fuel bound oxygen may reduce sooting combustion, and attract wide attention. The variation of thermophysical properties with temperature is essential for accurately modeling the combustion and emission characteristics of biodiesel fuelled diesel engines. Hence, the current paper attempts to predict the thermo-physical properties such as density, viscosity, specific heat, thermal conductivity, latent heat of vaporization, vapor pressure, mass diffusivity etc., and their variation with respect to the temperature following a machine learning approach for biodiesel fuels. Twenty feedstock samples are chosen for predicting the biodiesel thermo-physical properties and are validated with the available experimental data within a maximum error of 14 %. To evaluate the thermo-physical properties of a variety of feedstock, the predicted data are used for training an artificial neural network (ANN) and the developed ANN function is used for generating the various thermophysical properties of biodiesel fuels based on their composition and temperature. A good agreement is observed between the predicted and ANN results with a maximum mean absolute percentage error of 10 %. Hence in the current work, a collective mathematical modeling approach is proposed to accurately determine the spray and combustion-related fuel properties. The proposed model provides the various liquid and vapor properties and their variation with temperature which could be effectively employed for detailed spray and biodiesel-combustion modeling. An exhaustive data generation of eleven major liquid and vapour properties of twenty biodiesel fuels within the actual temperature range from 300 K to their respective critical temperature is presented.

MECHANISM OF DETONATION FORMATION IN THE PROCESS OF VIBRATION COMBUSTION

Based on thermodynamic analysis of combustion processes, we build a new model of laminar combustion process of vibration combustion. If the passive component velocity for the two-component mixture is controlled at the inlet (the interior energy is pumped at the inlet of the combustion chamber), high-frequency resonance oscillations of vibration combustion are shown to develop depending on the structure of the standard chemical potential. The resonance is driven by hydrodynamic instability. Numerical experiment models the regimes of resonance with pumped internal energy, the nature of their nucleation depending on the structure of the standard chemical potential is revealed. For low temperatures, the appearance of detonation combustion with substantial pressure increase is established near resonance.

Solid Digestate—Mathematical Modeling of Combustion Process

The combustion of waste biomass is becoming a key challenge for the energy sector, especially in times of growing energy demand and increasing environmental awareness of society. Processing such fuels is usually demanding. Mathematical modeling makes it possible to adapt the course of the process. The best option is to use appropriate fuel mixtures. The aim of this work was to develop a simple model that would allow the pre-selection of the mixture of two types of digestate. Residues from methane fermentation of maize and apple pomace were used in the study. The paper presents both a mathematical model and laboratory tests. The practical part was to check the validity of the model estimates. The model works on the basic data from physicochemical analysis. Laboratory tests included combustion of the samples of different mixtures. We used image analysis of thermograms to determine changes during combustion, which allowed us to determine when and where the main combustion occurs. Results show that a simple mathematical model is able to estimate the course of the combustion of a fuel particle.

Experimental and Mathematical Investigation of the Thermophysical Properties of Coal–Water Slurries Based on Lignite

The burning of organic fuel is one of the main factors influencing the greenhouse effect on the climate of the planet. The article examines the influence of the properties of lignite and coal–water slurries on the amount of carbon dioxide molecules formed as a result of chemical reactions. The authors give an overview of the results of other researchers in recent years and give the results of their research and development in the field of burning lignite and coal–water slurries in industrial recycling plants. The authors present the results of experimental studies of the thermophysical properties of coal and a coal–water mixture. The results obtained were compared with the results of calculations using a mathematical model and the results of numerical modeling in Ansys. New methods of approximation of step functions were used for the mathematical model. These methods make it possible to reduce errors in the approximation of the functions of the thermal properties of coal. The proposed methods do not have the disadvantages of traditional decompositions of step functions into Fourier series and can be used in problems of mathematical modeling of a wide class of processes and systems. In particular, when determining the coefficient of kinematic viscosity, ash content, and humidity by the method of approximation of the obtained data, the use of new mathematical methods makes it possible to reduce the error in calculations. In addition, data on numerical modeling of hydraulic transport and combustion processes are provided, and a data validation procedure is carried out. The data convergence shown and their location in the selected band of uncertainties satisfy the requirements for verification of experimental data adopted in the European Union and in the Eurasian Union.

Determination of Arrhenius parameters for advanced kinetic model used in CFD modeling of the wood pellet combustion process

With the increased popularity of using wood stoves for household heating in recent years, numerous experimental research projects have been launched with the goal of generating cleaner and more efficient stove designs. This work is focused on mathematical modeling of combustion process in low-power residential heating appliance (small-scale stove) fuelled by different wood pellets (WP1-Beech (hardwood) and WP2-Pine (softwood)). Kinetic model scheme that encompasses determination of Arrhenius parameters was proposed for applied Finite rate/Eddy Dissipation approach. Types of wood pellets have been combusted on the experimental stand which is equipped with a set of temperature sensors and exhaust analyzer. A comparison of results obtained from combustion in the heating unit has been performed to find relations between established kinetics of devolatilization for various wood pellets and to determine exhaust composition, arising from oxidation reactions. Numerical modeling using computational fluid dynamics (CFD) has been performed for the char and CO oxidations to supplement the experimental results. Due to limitations on installed stove such as poor design, air supply, fume extraction, or heat exchanger can lead to excessive CO emissions or lower energy efficiency. Outcomes show that it is crucial to minimize unused stove volume and to enhance gaseous mixing for reduction of CO emissions, while maintaining sufficiently high temperatures for supporting fast oxidation reactions. Results of comparisons of conducted analyses can be useful in areas related to process optimization and improvement of combustion and devolatilization reaction conditions in the small scale heating units.

Thermogravimetric characteristics and kinetic modeling of Piptocoma discolor pyrolysis and combustion processes to contribute to its use as a renewable energy source in the Ecuadorian Amazon region

Thermogravimetric characteristics and kinetic modeling of Piptocoma discolor pyrolysis and combustion processes to contribute to its use as a renewable energy source in the Ecuadorian Amazon region

Kinetics and modeling of combustion processes for various waste products

Kinetics and modeling of combustion processes for various waste products